Description

The gem's extconf.rb is not a native-extension build script. It contains a base64-encoded Ruby payload that, after gating on anti-analysis checks, downloads and executes an attacker-controlled shell script at install time. The anti-analysis gate inspects CI environment variables, hostname patterns (uvm/firecracker/sandbox/vagrant), username patterns (uA\d+, sandbox/tester/analys/scanner), working-directory prefixes (/tmp, /var/tmp, /opt/rubygems, /workspace), /proc/uptime (>1800s), and the presence of developer artifacts (~/.ssh, ~/.gitconfig, ~/.npmrc, ~/.gem/credentials, ~/.bundle) to restrict execution to real developer machines. When the gate passes, extconf.rb forks a detached process that sleeps 20-40 minutes, then reconstructs a URL by XOR-decoding a hex blob with key 'usv\x9a' resolving to http://45.138.12.177:8092/wgkit.tar.gz, downloads the archive to /tmp/.w1.tgz with no TLS and no integrity check, extracts it, and runs bash /tmp/.w1/wg_install.sh via system(). The package name is a typo of 'crypto-toolbox'. The combination of obfuscated URL reconstruction, bare-IP plaintext HTTP delivery, detached delayed execution, sandbox-evasion gating keyed on developer-only artifacts, and execution of arbitrary attacker-supplied bash during gem install is an install-time dropper on the installer's host.

The OpenSSF Package Analysis project identified 'crylto-toolbox' @ 1.0.0 (rubygems) as malicious.

It is considered malicious because:

The package executes one or more commands associated with malicious behavior.

Mitigation

Aliases

References